1. Field of the Invention
This invention relates to a hub assembly, more particularly to a hub assembly for a bicycle.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a bicycle hub assembly 10 disclosed in Taiwanese patent no. I335276 includes a hub shell 11, an annular ratchet member 12, and three pawl units each having a pawl 13 and a biasing member 14. The hub shell 11 has an inner tubular wall surface 111 which has three retreat bores 112 each having first and second retaining regions 113, 114. The annular ratchet member 12 has a plurality of cavities 121 in an outer surface thereof. The pawl 13 is inserted into the respective retreat bore 112, and has a pivot end 131 and a pawl end 132. The pivot end 131 is pivotable relative to the first retaining region 113 of the respective retreat bore 112. The pawl end 132 is movable between driven and idle positions. The biasing member 14 has a first segment 141 which is retained in the second retaining region 114 of the respective retreat bore 112, and a second segment 142 which abuts against the pawl end 132 of the respective pawl 13 so as to bias the pawl end 132 from the idle position, where the pawl end 132 is in a non-engaged state, to the driven position, where the pawl end 132 is engaged with the corresponding cavity 121. By virtue of such configuration, the hub shell 11 can foe driven to rotate with the annular ratchet member 12 only when the annular ratchet member 12 rotates in a clockwise or counterclockwise direction so as to engage the pawl ends 132 of the pawl units. However, the pawl units are inconvenient to install since the pawl 13 and the biasing member 14 of each pawl unit need be separately inserted into the respective retreat bore 112.
FIGS. 3 and 4 show another conventional bicycle hub assembly 20, which is disclosed in Taiwanese utility model no. M273524, and which includes a hub shell 21, an annular ratchet member 22, and a plurality of pawl units 23. Each pawl unit 23 includes a sleeve 24, a copper piece 25, a biasing member 26, and a pawl member 27. The sleeve 24 is inserted into a respective sleeve-receiving cavity 211 in the hub shell 21. The copper piece 25 is disposed to abut against a wall of a pawl-receiving recess 212 in communication with the sleeve-receiving cavity 211. The pawl member 27 includes a main body 270 and a pivot axle 271. The main body 270 includes a pivot end 273 which is pivotable about a pivot axis, and an opposite pawl end 274 formed with a slit 272 and engageable with the annular ratchet member 22. The pivot axle 271 extends from the pivot end 273 along the pivot axis and is insertable into and rotatable relative to the sleeve 24. The biasing member 26 has a looped segment 260 sleeved on the pivot axle 271, a first end segment 261 abutting against the inner face of the copper piece 25, and a second end segment 262 engageable with the slit 272, thereby biasing the pawl end 274 to engage the annular ratchet member 22. However, the installation of the pawl units 23 is still complicated. In addition, as the slit 272 is located at a lateral side of the main body 270 and is spaced a relatively large distance from the pivot axle 271, the biasing force of the biasing member 26 exerted through the second end segment 262 acts on only the lateral side of the main body 270, so that the engagement between the annular ratchet member 22 and the respective pawl member 27 is not steady.